Flanged interbody fusion device

ABSTRACT

Methods and devices are disclosed for treating the vertebral column. An implant for treating the spine is provided comprising at least two articulations between the spacer and the bone facing surface of the fixation plate. Another implant for treating the spine is also provided, comprising two or more fixation plates attached to a spacer with two or more articulations, wherein the fixation plates are independently movable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/748,333, filed Mar. 26, 2010, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/164,029 filed onMar. 27, 2009, the disclosure of each is incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to systems and methods for performingspinal fixation and, in particular, to interbody spacer devices.

Description of the Related Art

Advancing age, as well as injury, can lead to degenerative changes inthe bones, discs, joints and ligaments of the spine, producing pain andinstability. Under certain circumstances, alleviation of the problemscan be provided by performing spinal fusion. Spinal fusion is a surgicaltechnique where two or more vertebrae of the spinal column are fusedtogether to eliminate the motion between the fused vertebrae. Spinalfusion is used to treat conditions where the spine exhibits instability.Spine instability may result from causes such as fracture, scoliosis andspondylolisthesis, where one or more vertebrae move in a forwarddirection relative to the other vertebrae. Spinal fusion with discectomyis also performed for herniations of the discs. This surgery involvesremoval of the affected disc and fusion of the adjacent vertebrae.Traditionally, bone grafts have been used to fuse the vertebrae, butvarious types of vertebral implants have also been used.

The use of bone plate and bone screw fixation systems for treatinginjuries to bones is well established. In most instances, a bone plateis positioned over and surrounding the bone injury area and secured tothe bone. The bone plate is secured to the bone by bone screws or othersimilar fasteners inserted through holes in the bone plate and into thebone itself. The screws are tightened so that the bone plate holds thebone to be treated in place in order to insure proper healing. Earlyfixation devices tended to be applicable only to long bone injuries withonly limited uses for lower lumbar spinal injuries and disorders. Theuse of plate/screw fixation systems later expanded, however, to includemore uses for spinal injuries, including fusion of vertebrae includingfixation devices for treating cervical vertebrae injuries.Notwithstanding the foregoing, there remains a need for improved methodsand devices for treating spinal instability.

In existing spinal fusion implants there have also been problems withloosening and backing out of screws, especially in the cervicalvertebrae where the screws can back out into the patient's throat area.Backout is the exhibited tendency of bone screws, which affix the boneplate to the bone(s), to loosen with respect to both the plate and bone,resulting in poor fixation, fusion and ultimately, healing. Essentially,this loosening of the bone screw causes the screw to work itself out ofthe bone into which it is implanted. This results in the bone platebeing poorly fixed in place thus becoming devoid of its fixationcapabilities. Usually, backout is caused by the chronic stress of bodilymovement. While such loosening can be benign if limited in scope, it canlead to complications such as complete failure of the fixation device orincomplete bone fusion. Backout is particularly prevalent in areas ofhigh bodily stress and movement, such as the spine.

To alleviate backout and its associated problems, current systemsutilize secondary locking screws, locking collars or other secondarylocking devices that hold the bone screws in place after deploymentwithin the bone. In most systems, the bone screw is affixed into thebone through an opening in a bone plate. A locking device is theninserted into the bone screw. The locking device engages the head of thebone screw and is tightened which results in the bone screw being fixedin place within the bone, thus preventing backout.

While a locking screw or collar can alleviate backout, successful use ofsuch locking device systems in the anterior cervical spine isparticularly difficult because of anatomic constraints. Systems usingmultiple types of screws or collars to hold the bone screw in place aredifficult to deploy within the confines of a small operating areaavailable at the cervical spine. Furthermore, due to the small operatingarea, the surgeon implanting the device has great difficulty determiningif the device is properly deployed. Any instrumentation implanted in theregion must be minimally intrusive, yet have adequate strength towithstand the biomechanical loads to which it will be subjected. Thus,while current systems can help reduce instances of backout, theircomplex nature makes proper deployment very difficult and increases thechance of surgical error.

There is a need for an implant having a locking mechanism that can beeasily and reliably locked in place to prevent the loosening of andbacking out of the bone screws used to attach the implant to thevertebrae in the anterior aspect of the cervical, thoracic, and lumbarspine.

There is also a need for implants that can be implanted along a seriesof adjacent vertebrae. Implants adapted for use in the lumbar spine andthe thoracic spine become much less usable in the cervical spine becauseof differences in anatomy. In the lumbar spine, the disc spaces areabout 25% as tall as the vertebral bodies (i.e., the vertebral bodiesare generally four times taller than the intervening disc space). In thecervical spine, the disc space can be 50% of the height of the vertebralbodies. The disc spaces in the cervical spine are generally not greaterthan 7 or 8 mm tall in most people.

Attachment of one fixation plate between two vertebrae often preventsthe attachment of additional fixation plates between one of twovertebrae and an adjacent vertebra. This is especially true in thecervical spine region. The attachment of one fixation plate will reducethe surface area available to attach another fixation plate due to thesmall size of the cervical vertebrae and the minimum size required foreach fixation plate. Because of this limitation in existing spinalfixation devices, treatment of spinal disorders may be suboptimalbecause disease in adjacent vertebrae cannot be treated adequately.

SUMMARY OF THE INVENTION

Devices and methods are disclosed for treating the vertebral column. Anintegrated fixation plate and spacer is provided with at least twoarticulations between the fixation plate and spacer. In someembodiments, an implant for treating the spine is provided comprising afixation plate having an access surface and a bone facing surface, anupper portion and a lower portion, a spacer, and at least twoarticulations between the spacer and the bone facing surface of thefixation plate. In some embodiments, the at least two articulationsprovide for pivotable articulation and anterior-posterior movementbetween the spacer and the fixation plate.

In some embodiments, an implant for treating the spine is provided,comprising two or more fixation plates, a spacer, and two or morearticulations between the spacer and the two or more fixation plate,wherein the two or more fixation plates are independently movable.

In some embodiments, a method for treating a spine is provided,comprising: providing an implant for treating the spine comprising afirst and a second fixation plates, a spacer, and a first and a secondarticulations between the spacer and the first and the second fixationplates, wherein the fixation plates are independently movable, insertingthe spacer into an intervertebral space between a first vertebra and asecond vertebra, positioning the first fixation plate to lie generallyflat on the first vertebra, attaching the first fixation plate to thefirst vertebra, positioning the second fixation plate in generally theopposite direction as the first fixation plate to lie generally flat onthe second vertebra, and attaching the second fixation plate to thesecond vertebra.

The above embodiments and methods of use are explained in more detailbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and method of using the invention will be betterunderstood with the following detailed description of embodiments of theinvention, along with the accompanying illustrations, in which:

FIG. 1 is a lateral elevational view of a portion of the vertebralcolumn.

FIGS. 2A and 2B are superior and lateral elevational views of a thoracicvertebra.

FIG. 3 illustrates a superior elevational view of a cervical vertebra.

FIG. 4 represents a superior elevational view of a lumbar vertebra.

FIGS. 5A to 5D are various views of an embodiment of a pivotal fixationplate and spacer device.

FIGS. 6A to 6D are various views of an embodiment of an integratedfixation plate and spacer device with at least two articulations.

FIGS. 7A to 7D are various views of an embodiment of an integratedfixation plate and spacer device with more than one plate.

FIG. 8 is an isometric elevational view of an embodiment of a fastenerretaining assembly.

FIG. 9 is a cross-sectional view of a fixation device with the fastenerretaining assembly of FIG. 8 and an inserted screw.

FIG. 10A is a cross-sectional view of another embodiment of a fastenerwith an expansion ring. FIG. 10B is an exploded view of the fastener andexpansion ring in FIG. 10A.

FIG. 11 is a cross-sectional view of an embodiment of a fastener with anexpansion ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A. Anatomy of the Spine

As shown in FIG. 1, the vertebral column 2 comprises a series ofalternating vertebrae 4 and fibrous discs 6 that provide axial supportand movement to the upper portions of the body. The vertebral column 2typically comprises thirty-three vertebrae 4, with seven cervical(C1-C7), twelve thoracic (T1-T12), five lumbar (L1-15), five fusedsacral (S1-S5) and four fused coccygeal vertebrae. FIGS. 2A and 2Bdepict a typical thoracic vertebra. Each vertebra includes an anteriorbody 8 with a posterior arch 10. The posterior arch 10 comprises twopedicles 12 and two laminae 14 that join posteriorly to form a spinousprocess 16. Projecting from each side of the posterior arch 10 is atransverse 18, superior 20 and inferior articular process 22. The facets24, 26 of the superior 20 and inferior articular processes 22 form facetjoints 28 with the articular processes of the adjacent vertebrae.

The typical cervical vertebrae 30, shown in FIG. 3, differ from theother vertebrae with relatively larger spinal canals 32, oval shapedvertebral bodies 34, bifid spinous processes 36 and foramina 38 in theirtransverse processes 40. These foramina transversaria 38 contain thevertebral artery and vein. The first and second cervical vertebrae alsofurther differentiated from the other vertebrae. The first cervicalvertebra lacks a vertebral body and instead contains an anteriortubercle. Its superior articular facets articulate with the occipitalcondyles of the skull and are oriented in a roughly parasagittal plane.The cranium is able to slide forward and backwards on this vertebra. Thesecond cervical vertebra contains an odontoid process, or dens, whichprojects superiorly from its body. It articulates with the anteriortubercle of the atlas, forming a pivot joint. Side to side movements ofthe head occur at this joint. The seventh cervical vertebra is sometimesconsidered atypical since it lacks a bifid spinous process.

Referring to FIG. 4, the typical lumbar vertebrae 42 is distinguishablefrom the other vertebrae by the absence of foramina transversaria andthe absence of facets on the surface of the vertebral body 44. Thelumbar vertebral bodies 44 are larger than the thoracic vertebral bodiesand have thicker pedicles 46 and laminae 48 projecting posteriorly. Thevertebral foramen 50 is triangular in shape and larger than the foraminain the thoracic spine but smaller than the foramina in the cervicalspine. The superior 52 and inferior articular processes (not shown)project superiorly and inferiorly from the pedicles, respectively.

B. Flanged Spacer

In some embodiments, an interbody vertebral implant 100 can be provided.As shown in FIGS. 5A through 5D, in some embodiments, the implant 100can comprise a stabilization or fixation plate 102 having an upperportion 104 and a lower portion 106, and a bone facing surface 108 andan access surface 110. In use, typically the bone facing surface 108 canactually contact the vertebral bone surface, but in other embodiments,other structures or components can lie in between the bone facingsurface 108 and the bone surface of the vertebra. Each upper portion 104and lower portion 106 can have one or more spaces or holes 112 orientedbetween the bone facing surface 108 and the access surface 110 that areconfigured to accept screws and/or other attachment devices foranchoring the implant 100 to the vertebral bone. One or more spacers orspacing structures 114 can be located on the bone facing surface 108 ofthe fixation plate 102. The spacers 114 can be typically integrated withthe fixation plate 102 about the bone facing surface 108.

1. Spacer Component

The spacer can comprise any structure configured to maintain aseparation and resist compression between two adjacent vertebral bodies.The spacer can have any of a variety of overall shapes, including butnot limited to a rectangular box, a trapezoidal box, H-shaped, O-shaped,V-shaped, with or without one or more lumens within the spacingstructure. As shown in FIGS. 5A through 5D, the spacer 114 can have abase 116, a superior surface 118 and an inferior surface 120, and sidesurfaces 122, 124, and a posterior surface 126. Each surface 118, 120,122, 124, 126 need not be flat, and can be curved or undulating or anycombination thereof. The upper and lower surfaces 118, 120 can beconfigured for facing the superior and inferior vertebral bodies 8 or 34adjacent to an implantation site. The relative configuration of theupper surface 118 and lower surface 120 can vary, depending upon therelative position desired between the two adjacent vertebrae, theanatomical shape of the vertebrae, ease of insertion of the implant andother factors. For example, if a neutral vertical alignment is desiredbetween two vertebrae, the upper and lower surfaces 118, 120 can havegenerally parallel planar orientations. If a non-neutral alignment isdesired, for instance to maintain a natural spinal curvature in thecervical region, the upper and lower surfaces 118, 120 can have awedge-like relationship to allow fixation of the vertebrae in thedesired non-neutral position. A non-neutral alignment with respect tothe anterior-posterior direction can also be used to compensate forexcessive lordosis or kyphosis in other portions of the vertebralcolumn. The height of the spacing structure 114 at any section betweenthe upper and lower surfaces 118, 120 can be further configured toaccommodate degenerative changes or anatomical anomalies to providefixation in the desired relative position. Likewise, the side surfaces122, 124 of the spacing structure 114 can be generally parallel orskewed. In some embodiments, the side surfaces 122, 124 of the implant100 taper with increasing distance from the base 116 of the implant 100.A tapered spacing structure can facilitate insertion of the implant 100into the intervertebral space. In other embodiments, the one or moreside surfaces can flare distally or have both tapering and flaringportions.

FIGS. 5A through 5D illustrate an embodiment comprising a spacer 114with windows or holes 146, 152 between the outer side surfaces 122, 124and inner side surface 150 of the posterior member. These windows orholes can allow bony growth into the windows or holes. The space 146,152 within and/or between the posterior members can also be filled withgraft materials (not shown). The graft material can be an autograft,allograft, xenograft or synthetic material. Synthetic graft material canbe ceramic-based, silicon-based or calcium-based. The graft material canalso include osteoinductive factors to promote bone ingrowth. Oneskilled in the art will appreciate that there are many varieties ofsynthetic graft materials and constituents that can be used between orabout the hyoid bone segments.

One or more surfaces of the implant can also have surface projections,indentations, or holes or pores that can further alter thecharacteristics of the implant. Referring to FIGS. 5A through 5D, insome embodiments, angled projections, barbs, teeth 154 or rampedsurfaces which incline outwardly from one or more spacer surfaces towardthe fixation plate 102 can be provided on one or more surfaces thatallow insertion of the spacing structure in one direction but resistmovement in the opposite direction. These teeth 154 can be advantageousin reducing the migration of the device out of the intervertebral space.Improved fixation of the spacer 114 can maintain device position duringdrilling of the screw holes into the vertebral bodies, and can alsoreduce the forces acting upon the screws or other retaining structures,thereby reducing the risk of backout. The teeth 154 are preferablyprovided on the superior and/or inferior surfaces 118, 120 of the spacer114, but other surfaces can also have teeth or other tissue engagementstructures.

In some embodiments, the tissue engagement structures can be combinedwith indentations, holes or pores for allowing bony ingrowth or fillingwith bony matrix or graft materials as previously described. These holescan be utilized with other surface features to further enhance insertionand stabilization of the implant.

In some embodiments, the spacer can have a height of about 4 mm to about50 mm, or preferably about 4 mm to about 12 mm. In some embodiments, thespacer can have a height of about 6 mm to about 9 mm. In someembodiments, the spacer can have a length as measured from the bonefacing surface of the fixation plate to the most posterior end of thespacer of about 5 mm to about 25 mm. In some embodiments, the spacerlength can be about 10 mm to about 15 mm. The width of the spacer can begenerally about 5 mm to about 25 mm, and in some situations, about 10 mmto about 15 mm. One skilled in the art can dimension the spacer basedupon the implantation location and specific vertebral morphology,neurological anatomy and disease state.

The spinal fusion implant can include, be made of, treated, coated,filled, used in combination with, or contain artificial or naturallyoccurring materials suitable for implantation in the human spine. Thesematerials can include any source of osteogenesis, bone growth-promotingmaterials, bone derived substances, bone morphogenetic proteins,hydroxyapatite, genes coding for the production of bone, and boneincluding, but not limited to, cortical bone. The implant can also beformed of material such as metal including, but not limited to, titaniumand its alloys, surgical grade plastics, plastic composites, ceramics,or other materials suitable for use as a spinal fusion implant. In someembodiments, the device can comprise a radiolucent material, aradio-opaque material, or a combination thereof. A device that ispartially or completely radiolucent can be advantageous when evaluatingthe effect of the implant post-implantation. Many existing spinalfixation plates and/or spacers obscure visualization of the vertebrae,which can complicate post-operative treatment, diagnosis and prognosisof the patient's condition. The implant can include at least in partmaterials that are bioabsorbable in the body. The implant of thedescribed embodiments can be formed of a porous material or can beformed of a material that intrinsically participates in the growth ofbone from one of adjacent vertebral bodies to the other of adjacentvertebral bodies. The implant can be treated with, coated with, or usedin combination with substances to inhibit scar tissue formation. Theimplant of the described embodiments can be modified, or used incombination with materials to provide antibacterial properties, such as,but not limited to, electroplating or plasma spraying with silver ionsor other substance. The implant can optionally comprise an electricalsource to provide ionophoresis of the silver ions into the surroundingtissue to prevent infection. The antibacterial properties can includebactericidal and/or bacteriostatic characteristics. Similarly,anti-fungal characteristics can also be provided. Any of these materialsas appropriate can be used at any time after the implant(s) areinserted.

2. Fixation Component

The fixation plate can have a generally flat configuration, curvedconfiguration or combination thereof. Optionally, each surface of thefixation plate can also have a generally flat or curved configuration orcombination thereof. Each surface of the fixation plate need not havethe same configuration. The edges of the fixation plate can optionallybe rounded, smoothed or polished. In some embodiments, the flange can bedimensioned such that the flange extends about 2 mm beyond the edges ofthe base of the spacer. In some embodiments, the fixation component canbe dimensioned to extend generally about 1 mm to about 20 mm beyond theperimeter of the spacer component at its interface with the fixationplate. In other embodiments, the flange can extend by 3 mm or 4 mm ormore beyond the spacer base. The flange may or may not extend uniformlyalong the spacer edges. The shape of the flange can be different fromthe shape of the spacer base.

In some embodiments, illustrated in FIGS. 5A through 5D, the flange 102of implant 100 can have a general square or rectangular shape and isdimensioned to allow stable attachment of the implant 100 to theadjacent vertebral bodies 8. The corners where any two sides of theflange meet can be angled, rounded or curved. The flanged implant 100depicted in FIGS. 5A through 5D can comprise rounded corners. In otherembodiments, the flange 102 can comprise any of a variety of othershapes, including trapezoids, circles, ovals, polygons or other closedshapes. The flange 102 may or may not have a symmetrical configurationwith respect the upper and lower portions and/or the left and rightportions of the flange.

In some embodiments, the average thickness of the fixation plate can bewithin the range of about 1 mm to about 5 mm. In other embodiments, theaverage thickness of the fixation plate can be within the range of about1.5 mm to about 3.0 mm. The thicknesses of the fixation plate need notto be uniform. In some embodiments, the fixation plate can beconformable to the vertebral surfaces of the implantation sites.

In some embodiments, the spacer component can be attached to a fixationcomponent comprising a mesh or lattice. The fixation component can alsobe made from a material that is the same or different from the spacercomponent. In some instances a fixation component and a spacer componenthaving different materials can be beneficial because the spacercomponent can be configured to withstand compressive forces while thefixation component is configured to withstand primarily tension forces.The fixation component can comprise a polymer, a woven material, or acombination thereof.

In some embodiments, the flange 102 can be configured for positioningacross an intervertebral space such that the upper portion 104 of theflange 102 can be adapted to contact the superior vertebra and the lowerportion 106 of the flange 102 can be adapted to contact the inferiorvertebra about an intervertebral space. In some embodiments, the flange102 can be configured to contact a single vertebra about anintervertebral space, or more than two vertebrae. In some embodiments,the flange 102 can span two or more intervertebral spaces. Typically,the implant 100 can be adapted for positioning about the anteriorsurface of the vertebrae, along the anterior surfaces of vertebralbodies. In some instances, the flange 102 of the implant 100 can also beconfigured to contact other vertebral structures such as the pedicles,transverse processes, facet joints, superior and inferior articularprocesses and spinous processes. In still other embodiments, the implant100 can be configured to attach to these vertebral structures withoutattaching or contacting the vertebral bodies.

Referring back to FIGS. 5A through 5D, each upper portion and lowerportion of the fixation plate 102 can have one or more spaces or holes112 oriented between the bone facing surface 108 and access surface 110that are configured to accept screws and/or other attachment elementsfor anchoring the implant to the vertebral bone. In some embodiments,one or more bone screws 158 configured for insertion through one or morescrew holes 112 in the fixation plate 102 are provided.

Each hole 112 of the flange or fixation plate 102 need not have the sameconfiguration or size. The holes 112 can be round in cross-section anddimensioned to allow passage of a screw body therethrough whileresisting passage of the screw head completely through the hole 112. Insome embodiments, at least a portion of the hole 112 can have anon-round cross-section, such as an oval, square, rectangle, polygon orother closed shape. The inside surface of the holes 112 can be coveredwith a lubricious coating to facilitate insertion and/or movement of ascrew or other attachment device through the hole.

In some embodiments, the flanged interbody device comprises a polyarylpolymer, including but not limited to PEK, PEEK, PEKK, PEKEKK or a blendthereof, and the insert comprises a titanium or titanium alloy. Othercombination can also be used as is known by those with skill in the art.

C. Implantation Procedure

In some embodiments, the patient can be intubated and general anesthesiacan be achieved. The patient can be prepped and draped in the usualsterile fashion. An anterior approach to the spine can be used to exposethe anterior vertebral bodies. Many anterior approaches to the vertebralcolumn are described in various medical texts such as Campbell'sOperative Orthopaedics, 10th ed., edited by Canale et al., pp.1569-1588, herein incorporated by reference. In some embodiments, theupper cervical spine can be accessed. The anterior upper cervical spinecan be accessed by a transoral or retropharyngeal route, or by using asubtotal or extended maxillotomy. In other embodiments, the lowercervical spine, cervicothoracic junction, thoracic spine, thoracolumbarjunction, lumbar region, lumbosacral junction, sacrum or combination ofthe above regions can be accessed.

The intervertebral space can be debrided. In some embodiments, theflanged interbody implant can be packed with natural or artificial bonematrix and/or other osteogenesis factors and inserted into theintervertebral space. The flange can be positioned against the anteriorcervical vertebral bodies and attached with screws or anchors. Theoperative site can be irrigated with antibiotics and the operative fieldcan be sutured closed. The vertebral column can be accessed and one ormore intervertebral spaces can be identified and accessed. In someembodiments, two or more intervertebral spaces can be accessed, and instill other embodiments, two or more adjacent intervertebral spaces canbe accessed. The operative site can be rinsed with antibiotic solutionand the operative field can be closed in layers.

In another embodiment, a method for treating a spine can comprise thesteps of providing an implant for treating the spine comprising two ormore fixation plates, a spacer, and two or more articulation between thespacer and the two or more fixation plates, wherein the fixation platesare independently movable. The spacer can be inserted into anintervertebral space between a first vertebra and a second vertebra. Oneof the fixation plates can be positioned to lie generally flat on thefirst vertebra and can be attached to the first vertebra. A secondfixation plate can be positioned in generally the opposite direction asthe first fixation plate to lie generally flat on the second vertebraand can be attached to the second vertebra. Any remaining fixationplates can further be positioned to lie generally flat on the first orsecond vertebra and attached to the vertebra.

In some embodiments, the method for treating a spine can furthercomprise providing a second implant for treating the spine comprisingtwo or more fixation plates, a spacer, and two or more articulationsbetween the spacer and the two or more fixation plates, wherein thefixation plates are independently movable. The spacer of the secondimplant can be inserted into a second intervertebral space between thesecond vertebra and a third vertebra, wherein the second intervertebralspace is next to the first intervertebral space along a vertebralcolumn. One of the fixation plates of the second implant can bepositioned to lie generally flat on the second vertebra andcomplementary to the second fixation plate of the first implant and canbe attached to the second vertebra. In embodiments with two fixationplates, when the left fixation plate of the first implant is fixed tothe second vertebra, the right fixation plate of the second implant canbe attached to the second vertebra, so the left fixation plate of thefirst implant is positioned next to the right fixation plate of thesecond implant on the second vertebra. A second fixation plate of thesecond implant can be positioned in generally the opposite direction asthe first fixation plate of the second implant to lie generally flat onthe third vertebra and can be attached to the third vertebra. In anotherembodiment, the method for treating a spine can further comprisesproviding a third or additional implants for treating the spine andimplanting according to the method for the second implant.

D. Pivot Plate

In some embodiments of the invention, the interbody spacer and thefixation plate can be configured to provide some degree of relativemovement between each other. By providing some relative movement betweenthe interbody spacer and fixation plate portions, the device can haveimproved securement to osseous structures with improved conformance tothe existing anatomy at the site of implantation. FIGS. 5A through 5Ddepict an embodiment comprising a hinge joint 128 oriented to allowpivoting of the fixation plate 102 relative to the spacer 114. In theillustrated embodiment, the hinge joint 128 is oriented to allowpivoting in the sagittal plane. In other embodiments of the invention,the hinge joint 128 can be oriented to allow pivoting in other planessuch as the transverse plane, coronal plane, or any plane in between thethree planes. The joint provided between the interbody spacer 114 andthe fixation plate 102 can be further configured to limit the range ofmovement provided. In other embodiments, the configuration of theinterbody spacer 114 and/or fixation plate 102 can restrict the relativerange of motion between the two components. Recesses in the fixationplate 102 or a size reduction or tapering of the interbody spacer 114about the movement joint 128 can provide clearance to allow greaterrange of movement between the fixation plate 102 and the spacer 114. Oneof skill in the art will understand that the movement joint 128 may beconfigured to vary other characteristics of the movement joint,including frictional resistance or ratchet-type resistance to movement.Although the hinge joint in FIGS. 5A to 5D are depicted in a symmetricposition on the interbody spacer and fixation plate, an eccentriclocation may be used.

Although a hinge-type movement joint is depicted in FIGS. 5A to 5D,other types of joints or connections between the interbody spacercomponent and fixation plate are also contemplated, including but notlimited to an elastomeric joint, a ball-and-socket joint, a slidingjoint, a rotatable articulation configured to allow reversibleseparation of the fixation plate and spacer, or one or more metalliccords embedded or attached between the fixation plate and interbodyspacer to allow limited polyaxial movement.

Moreover, although a single interbody spacer 114, fixation plate 102 andmovement joint 128 are depicted, other embodiments can have two or moremovement joints and wherein either the fixation plate and/or interbodyspacer can have a split configuration so that each split component hasits own movement joint and can independently move or pivot to provideadditional conformance to the existing anatomy.

In still other embodiments, the fixation plate 102 and/or interbodyspacer 114 can be configured with two or more subcomponents that areprovided with an intracomponent hinge or movement joint to providebetter conformance of the device to the existing anatomy. For example,the fixation plate component of the device can be configured as left andright subcomponents with a hinge joint in-between. In another example,the interbody spacer can have superior and inferior subcomponents with ahinge joint therebetween to allow pivoting of the superior and inferiorsurfaces of the interbody spacer. Depending on the orientation of thehinge joint, the superior and inferior surfaces of the interbody spacercan pivot laterally or in an anterior-posterior direction, or anydirection in-between.

E. Multi-Axial Movement Fixation Plate

In some embodiments, multiple joints between the interbody spacer andthe fixation plate can be configured to provide additional degrees ofmovement relative to each other. By providing adjustment of the fixationplate in multiple degrees of movement relative to the interbody spacer,securement to osseous structures can be improved while also improvingconformance to the existing anatomy at the site of implantation. FIGS.6A through 6D illustrate an implant 200 comprising a double hinge joint260 and single hinge joint 262 disposed to allow multiple degrees ofmovement. The double hinge joint 260 can move in a circular cam motionabout the longitudinal axis of single hinge joint 262, or in analternative description, the single hinge joint 262 can move in acircular cam motion about the longitudinal axis of the double hingejoint 260. The two hinge configuration can allow the spacer 214 and thefixation plate 202 to move in a circular and reciprocating movementrelative to each other. The combination of the double hinge joint 260and the single hinge joint 262 can permit the relative movement in boththe anterior-posterior and the superior-inferior directions. Both theinterbody spacer 214 and the fixation plate 202 can also have anadditional degree of pivotal movement about the hinge joints 262 and260. FIGS. 6A and 6B illustrate the device in the configuration wherethe distance between the spacer 214 and the fixation plate 202 is at itsminimum. FIGS. 6C and 6D illustrate the device in the configurationwhere the distance between the spacer 214 and the fixation plate 202 istoward its maximum.

In some embodiments, the hinge joints 260 and 262 can be oriented toallow similar movements in any plane such as the sagittal plane,transverse plane, coronal plane, or any plane in-between the threeplanes. In some embodiments, the hinge joints 260 and 262 providedbetween the interbody spacer 214 and the fixation plate 202 can beconfigured to limit the range of movement provided. In some embodiments,the configuration of the interbody spacer 214 and/or fixation plate 202can restrict the relative range of motion between the two components. Insome embodiments, recesses in the fixation plate 202 or a size reductionor tapering of the interbody spacer component 214 about the hinge joints260 and 262 can allow greater range of motion. The hinge joints 260 and262 can be configured to vary other characteristics of the movementjoints, including frictional resistance or ratchet-type resistance tomovement. Although the hinge joints in FIGS. 6A through 6D are depictedin a symmetric position on the interbody space and fixation plate, aneccentric location can be used.

Although hinge-type movement joints are depicted in FIGS. 6A to 6D,other types of joints or connections between the interbody spacercomponent and fixation plate are also contemplated, including but notlimited to elastomeric joints, ball-and-socket joints, sliding joints,rotatable articulations configured to allow reversible separation of thefixation plate and the spacer, or one or more metallic cords embedded orattached between the fixation plate and interbody spacer to allowlimited polyaxial movement.

The hinge-type movement joints depicted in FIGS. 6A to 6D canadvantageously allows the distance between the fixation plate 202 andthe spacer 214 to be adjusted by the surgeon. In this manner, a singledevice can be adapted to individual anatomies. This can reduce theamount of inventory needed.

F. Multiple Pivot Plates

In some embodiments, the implant can comprise two or more fixationplates with independent movement joints, wherein each fixation plate iscoupled to a separate movement joint that can independently move orpivot to provide additional conformance to the existing anatomy. FIGS.7A through 7D depict such an implant 400, comprising an interbody spacer414, a first fixation plate 470 coupled to the interbody spacer 414 by afirst hinge joint 464, and a second fixation plate 472 coupled to theinterbody spacer 414 by a second hinge joint 466. The hinge joints 464and 466 can allow the pivotal movement between the interbody spacer 414and the two fixation plates 470 and 472. In some embodiments, thefixation plates 470 and 472 can be pivoted to a predetermined position,such as generally parallel to the interbody spacer 414, so that thespacer 414 can present a low profile, as illustrated in FIGS. 7A and 7B.This configuration can be advantageous for insertion of the device intoan intervertebral space in the body. In some embodiments, the fixationplates 470 and 472 can be pivoted so that they extend away from theinterbody spacer 414, which can also advantageously serve insertion ofthe device. In some embodiments, the first fixation plate 470 can bepivoted to a position generally perpendicular to the interbody spacer414, and coupled with a first vertebra, and the second fixation plate472 can be pivoted in a direction opposite to the first fixation plate470 to a position generally perpendicular to the interbody spacer 414and coupled with a second vertebra. FIGS. 7C and 7D illustrate theimplant 400 in this configuration. In some embodiments, the first andsecond fixation plates 470 and 472 can be independently pivoted tovarious positions at certain angles relative to the interbody spacer 414for coupling with two adjacent vertebras.

In other embodiments, the hinge joints 464 and 466 can be oriented toallow pivoting in any plane such as the sagittal plane, transverseplane, coronal plane, or any plane in-between the three planes. Thejoints provided between the interbody spacer 414 and the fixation plates470 and 472 can be further configured to limit the range of movementprovided. In some embodiments, the configuration of the interbody spacer414 and/or fixation plates 470 and 472 can restrict the relative rangeof motion between the components. In some embodiments, recesses in thefixation plates 470 and 472 or a size reduction or tapering of theinterbody spacer component 414 about the movement joints 464 and 466 canallow greater range of motion between the components. The movementjoints 464 and 466 can be configured to vary other characteristics ofthe movement joint, including frictional resistance or ratchet-typeresistance to movement. In some embodiments, the joints 464 and 466 caneach comprise multiple joints to provide multi-axial motion, asdescribed above.

In other embodiments, the implant can include more than two fixationplates, with each fixation plate able to pivot to a position generallyperpendicular or at any angle to the interbody spacer and couple withthe first or second vertebra. Although the hinge joints in FIGS. 7Athrough 7D are depicted in a symmetric position on the interbody spacerand fixation plates, an eccentric location can be used.

Although a hinge-type movement joint is depicted in FIGS. 7A through 7D,other types of joints or connections between the interbody spacercomponent and fixation plates are also contemplated, including but notlimited to elastomeric joints, ball-and-socket joints, sliding joints,rotatable articulations configured to allow reversible separation of thefixation plate and spacer, or one or more metallic cords embedded orattached between the fixation plate and interbody spacer to allowlimited polyaxial movement. The above described spacer is particularlyuseful in embodiments in which a superior and inferior vertebrae areseparated using pins or other devices. For example, in certainapplications (e.g., in the cervical spine) elongate pins can beimplanted into superior and inferior vertebrae and used as anchors toseparate the vertebra from each other. The elongate pins can beimplanted in an offset orientation, for example wherein a first elongatepin can be implanted on the left portion of a first vertebra and thesecond elongate pin can be implanted on the right portion of a secondvertebra. The above described embodiments allow the flanges 470, 472 tobe pivoted into the spaces on the vertebra not occupied by the pins.That is, one of the fixation plates can be positioned to lie generallyflat on the right portion of the first vertebra and can be attached tothe first vertebra. A second fixation plate can be positioned ingenerally the opposite direction as the first fixation plate to liegenerally flat on the left portion of the second vertebra and can beattached to the second vertebra.

G. Alternative Screw Locks

In addition to the embodiments of the screw retaining assembliesdescribed above, other screw retaining assemblies are also contemplatedand can be used with the interbody fusion devices previously described.The other screw retaining assemblies described below can also be usedwith other types of orthopedic and medical devices, as well asnon-medical applications, including but not limited to construction,home improvement, consumer appliance, electronic device and otherapplications.

1. Screw Retainer with Pivot Surface

FIGS. 8 and 9 depict some embodiments comprising an expandable fastenerretaining ring 310 residing partially within an expansion groove 312 ofa fastener lumen 112 and partially within the fastener lumen 112 itself.The retaining ring 310 can have a reduced configuration and an expandedconfiguration but can be biased to the reduced configuration. Theretaining ring 310 can have a retaining segment 314 and a pivot segment316. Referring to FIG. 9, the retaining segment 314 can have an enlargedouter diameter that is adapted to fit in an expansion groove 312. In theexpanded configuration of the retaining ring 310, the retaining segment314 can further expand into the expansion groove 312, thereby increasingthe inner diameter 318 of the retaining segment 314. The inner diameter318 of the retaining segment 314 can have a sloped inner surface 320that narrows from the proximal opening 322 of the retaining ring 310.The sloped surface 320 can facilitate expansion of the retaining segment314 as a fastener 158 is inserted through it. Once the fastener head 160has passed through the retaining segment 314 of the retaining ring 310,the inner diameter 324 of the polyaxial segment 316 of the retainingring 310 can be larger, allowing the fastener head 160 to reside in theretaining ring 310 without exerting an expansion force against theretaining ring 310. This can allow the retaining ring 310 to at leastpartially, if not completely, revert back to its reduced configuration.If backout forces are exerted on the fastener head 160, the fastenerhead 160 can abut a generally perpendicular retaining surface 232located at the transition from the inner diameters 318, 324 of theretaining and polyaxial segments 314, 316 of the ring 310 and can resistfastener head 160 backout.

The polyaxial segment 316 of the retaining ring 310 can comprise asloping reduced diameter 326 towards the distal opening 328 of theretaining ring 310, such that the smallest diameter of the polyaxialsegment 316 can be smaller than the largest diameter of the fastenerhead 160 and can prevent or resist the fastener head 160 from passingcompletely through the retaining ring 310. The slope of thecross-section through the retaining ring can be linear, curved, toothedor jagged or any other sloped surface.

2. Fastener Head Embedded Expansion Lock

In some embodiments, illustrated in FIGS. 10A and 10B, the fastener 330can comprise a secondary screw 332 and screw lumen 334 within thefastener head 336. An expandable ring 338 or disc, having a reduced andan expanded configuration, is provided within a groove 340 about thefastener head 336, with the expandable ring or disc biased to thereduced configuration. The groove 340 can be contiguous with screw lumen334 of the fastener head 336 at one or more openings 342, such that theportion 344 of the inner surface 346 of the expandable ring 338 or discpartially protrudes into the screw lumen 334 when the expandable ring338 or disc is in the reduced configuration. The secondary screw 332 ofthe fastener 330 can have an expansion section, typically the head 348of the secondary screw 332, which can have an outer diameter 350 that isgreater than the distance 352 within the screw lumen 334 where theexpansion ring 338 or disc protrudes into the screw lumen 334. When theexpansion section 348 of the secondary screw 332 is not in contact withthe inner protruding portions 344 of the expandable ring 338 or disc,the expandable ring 338 or disc is able to remain in the reducedconfiguration. When the expansion section 348 of the secondary screw 332is fully positioned against the protruding portions 344 of theexpandable ring 338 or disc, it can act against the expandable ring 338or disc and can cause the expandable ring 338 or disc to enlarge to itsexpanded configuration. In the expanded configuration, the outerdiameter 354 of the expandable ring 338 or disc can be greater than thelargest outer diameter of the remaining portions of the fastener 330. Inthe reduced configuration, the outer diameter of expandable ring or discmay or may not radially extend from out of the groove.

Referring to FIG. 11, the fastener 330 is preferably used in deviceshaving one or more fastener lumens 356 with a proximal diameter 358,middle diameter 360 and distal diameter 362, wherein the proximaldiameter 358 is greater than the distal diameter 362 but less than themiddle diameter 360, and wherein the proximal diameter 358 is less thanthe outer diameter 364 of the expandable ring 354 or disc in the reducedconfiguration. The outer diameter of the expandable ring 338 or disc, inthe expanded configuration, can be larger than the proximal diameter 358of the fastener lumen 356, thereby preventing or resisting backout ofthe fastener 330. In some embodiments, as shown in FIG. 10A, the screwlumen can be lined by an hole insert 366 having a similar relationshipof its proximal, middle and distal diameters. A hole insert 366 can bepreferred, for example, when the orthopedic device utilizing thefastener system comprises a material that may exhibit wear from themetallic fasteners. A hole insert 366 can be provided to protect againstsuch wear.

Referring again to FIG. 10A, the screw lumen 334 of the fastener 330 canextend distally from the openings 342 contiguous with the fastener headgroove 340 to allow the secondary screw 332 to completely reside withinthe screw lumen 334 in a position distal to the screw lumen openings 342and inner protrusions 344 of the expandable ring 338 or disc. Thisfeature can allow the fastener 330 to be attached to the desiredstructure without having to later insert the secondary screw 332 intothe fastener 330 to enlarge the expandable ring 338 or disc. Instead,once the fastener 330 is attached to the desired structure, thesecondary screw 332 need only be moved proximally in the screw lumen 334to act against the expandable ring 338 or disc and enlarge theexpandable ring 338 or disc to its expanded configuration and to retainthe fastener in place. By allowing the attachment of the fastener 330with the secondary screw 332 already in place, the use of fastener 330in cramped or limited access areas, such as the attachment of a cervicalfusion plate or interbody fusion device, need not attempt to maintain atiny secondary screw 332 on the end of an attachment device whileattempting to align the tiny secondary screw 332 with the screw lumen334 of the fastener head. The user of the fastener 330 only has to alignthe screwdriver of the secondary screw to the secondary screw in orderto manipulate it.

H. Conclusion

Although the present invention has been described in relation to variousexemplary embodiments, various additional embodiments and alterations tothe described embodiments are contemplated within the scope of theinvention. Thus, no part of the foregoing description should beinterpreted to limit the scope of the invention as set forth in thefollowing claims. For all of the embodiments described above, the stepsof the methods need not be performed sequentially.

What is claimed is:
 1. An implant for treating the spine, comprising: afixation plate having an access surface and a bone facing surface; aspacer; and at least two articulations between the spacer and the bonefacing surface of the fixation plate, a first articulation allowing for360 degrees of movement between the spacer and an intermediate member,and a second articulation allowing for movement between the intermediatemember and the fixation plate, each articulation comprising a separateaxis of rotation, wherein the at least two articulations are configuredto allow multiple degrees of rotation.
 2. The implant for treating thespine as in claim 1, wherein the at least two articulations provide foranterior-posterior movement between the spacer and the fixation plate.3. The implant for treating the spine as in claim 1, wherein anarticulation of the at least two articulations is a hinge joint.
 4. Theimplant for treating the spine as in claim 3, wherein the hinge jointhas a joint axis that does not intersect the fixation plate.
 5. Theimplant for treating the spine as in claim 3, wherein the hinge jointhas a joint axis configured to be perpendicular to a longitudinal axisof a vertebral column when implanted.
 6. The implant for treating thespine as in claim 1, wherein the axis of rotation of at least onearticulation does not intersect the fixation plate.
 7. The implant fortreating the spine as in claim 1, wherein the axis of rotation of atleast one articulation is parallel to the fixation plate.
 8. The implantfor treating the spine as in claim 1, wherein at least one articulationis configured to allow reversible separation of the fixation plate andspacer.
 9. The implant for treating the spine as in claim 1, wherein theat least two articulations comprise a single hinge joint and a doublehinge joint.
 10. The implant for treating the spine as in claim 9,wherein the double hinge joint is configured to move with 360 degrees ofmovement about the longitudinal axis of the single hinge joint.
 11. Theimplant for treating the spine as in claim 1, wherein the at least twoarticulations are configured to allow the spacer and the fixation plateto move in a reciprocating movement relative to each other.
 12. Theimplant for treating the spine as in claim 1, wherein the at least twoarticulations are configured to allow relative movement in both theanterior-posterior and the superior-inferior directions.
 13. An implantfor treating the spine, comprising: a fixation plate having an accesssurface and a bone facing surface, an upper portion and a lower portion;a spacer; at least one member interconnecting the fixation plate and thespacer; at least one articulation between the fixation plate and the atleast one member to allow movement about a first axis; and at least onearticulation between the spacer and the at least one member to allowmovement about a second axis; wherein the articulations provide for 360degrees of movement between the at least one member and the spacer, andmovement between the at least one member and the fixation plate; whereinin a first configuration, the distance between the fixation plate andthe spacer is at a minimum; wherein in a second configuration, thedistance between the fixation plate and the spacer is at a maximum. 14.The implant for treating the spine as in claim 13, wherein anarticulation of the at least one articulation between the fixation plateand the at least one member is a hinge joint or wherein an articulationof the at least one articulation between the spacer and the at least onemember is a hinge joint.
 15. The implant for treating the spine as inclaim 14, wherein at least one of the hinge joints has a joint axis thatdoes not intersect the fixation plate.
 16. The implant for treating thespine as in claim 14, wherein at least one of the hinge joints has ajoint axis configured to be generally perpendicular to a longitudinalaxis of a vertebral column when implanted.
 17. The implant for treatingthe spine as in claim 13, wherein an articulation of the at least onearticulation between the fixation plate and the at least one member is arotatable articulation comprising an axis of rotation or wherein anarticulation of the at least one articulation between the spacer and theat least one member is a rotatable articulation comprising an axis ofrotation.
 18. The implant for treating the spine as in claim 17, whereinthe axis of rotation of the rotatable articulation does not intersectthe fixation plate.
 19. The implant for treating the spine as in claim17, wherein the axis of rotation of the rotatable articulation isparallel to the fixation plate.
 20. The implant for treating the spineas in claim 17, wherein the rotatable articulation is configured toallow reversible separation of the fixation plate and spacer.
 21. Theimplant for treating the spine as in claim 13, wherein the first axisand the second axis are parallel.
 22. The implant for treating the spineas in claim 13, wherein the first axis and the second axis extendthrough the at least one member interconnecting the fixation plate andthe spacer.
 23. The implant for treating the spine as in claim 13,wherein the articulations comprise a single hinge joint and a doublehinge joint.
 24. A method for treating a spine, comprising: providingthe implant of claim 1, wherein the fixation plate further comprises anupper portion and a lower portion, wherein in a first configuration, thedistance between the fixation plate and the spacer is at a minimum,wherein in a second configuration, the distance between the fixationplate and the spacer is at a maximum; adjusting the implant to anyconfiguration between, or including, the first configuration and secondconfiguration; inserting the spacer into an intervertebral space betweena first vertebra and a second vertebra; attaching the upper portion ofthe fixation plate to the first vertebra; and attaching the lowerportion of the fixation plate to the second vertebra.